Why is my internet slow? Find the cause in 3 steps

1. Test over a cable first

Wi-Fi is one of the most common causes of slowdowns at home. Connecting your computer to the router with an Ethernet cable and testing on an idle line shows what the line really delivers. If the wired result is close to your plan, your line is fine and the slowdown happens inside your home.

Don't expect the exact figure: because of the addressing every packet carries, a 100 Mbps line shows at most 94.1 Mbps. We work it out in is 100 Mbps really 100. The other details of a good test are in how to run a speed test correctly.

2. Fast over a cable: the problem is at home

• Wi-Fi: distance, walls and neighbouring networks cut speed. Which band to pick and how to speed it up is in the Wi-Fi guide.
• Devices in use at the same time: the TV, phone backups and game downloads split the line; see shared connections.
• The device running the test: an old or overloaded device can't fill the line; the device guide shows how to tell.
• Battery saver: throttles the network and CPU on phones and laptops; see battery saver.

3. Slow over a cable too: the line, the time or the provider

If the wired result is also well below your plan, repeat it in the morning and in the evening. If mornings are low too, the problem is the line, the router or the provider. If only evenings are low, the provider's shared capacity is filling up.

In HIZTESTI's measurements typical download drops by 18% in the evening compared with the best hour of the night. We show why, and how to prove it to your provider, in why the internet slows in the evening. If mornings stay low as well, restart the router, swap the cable, and keep the result links to send to your provider.

Is it speed or responsiveness that's slow?

Not every slowdown is about speed. If the test shows a high speed but video calls freeze and games stutter, the problem is most likely response time. Three measures describe it:

• Ping: the round trip to the server. Typical fixed-line ping on HIZTESTI is 21 ms.
• Jitter: how much ping wobbles. A common cause of choppy video and audio.
• Packet loss: part of the data never arriving. It cuts out calls and makes characters teleport in games. The browser test can't measure it; the HIZTESTI apps also show loss during a test.

When response time soars only while the line is busy, that's a separate problem called bufferbloat, and if your router supports it, a setting can largely fix it.

Is your plan enough for what you do?

Everything may be measured correctly and the line may deliver its plan; then the question is the plan itself. Think about how many people do what at the same time. We explain the unit in what is Mbps, why upload matters for calls and backups in why upload speed matters, and what decides gaming in how much speed for gaming.

Run a test first to see where your result sits. Start a speed test